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35mm Shallow DOF adapters?!?!


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#1 Dennis Kisilyov

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Posted 13 February 2007 - 04:58 AM

I would have posted this in a Camera specific forum... but I think it applies to all lower priced HD cams.

Here goes a series of daft questions from yours truly.


1. Are all these 35mm/Cine lens adpters basically a ground glass which delivers the picture through the non-removable HD Camcorder lens like the Sony Z1U and HVX200 from Panasonic.

All the websites from micro35 and M2 are not specific about how these boxes in front of the lens work...


2. Is there any Cinema-like footage/shorts shot with-out these adapters in the Critique forums? From the 5k and under HD Cams? JVC/Pana/Sony?

3. What are the benefits? The CCD/CMOS sensor sizes seem to match 16mm and built in lenses are fast enough to handle semi shallow DOF.

4. Will non-adaptor and adaptor footage intercut well (not in the same scene/sequence)?

Or will it look so different from the ground glass adapter vs. just with the built-in lens that the audience would notice.

Not just in the same scene, but different scenes/sequences. In film world that would equate either using different stock in different scenes, or a B-camera thats different from A-camera.

5. How many stops of light do these things loose?

Even if using a T1.3 it would seem that the Adapter + Built in Lens would take out about 2-3 stops more making them hard to use in Low Light situations..


Sorry if this has been answered before, I searched and found many discussions on merits of one vs. the other. Not too many about general function of such devices.

Thanks in advance.


6. If it is a ground glass, how often do you have to clean it so that you don't end up with dust in the frame?
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#2 Troy Warr

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Posted 13 February 2007 - 06:49 AM

Hi Dennis,

> 1. Are all these 35mm/Cine lens adpters basically a ground glass which delivers the picture through the non-removable HD Camcorder lens like the Sony Z1U and HVX200 from Panasonic. All the websites from micro35 and M2 are not specific about how these boxes in front of the lens work...

For the most part. There's a decent Wikipedia article about how these work - it also mentions most of the major manufacturers making these adapters right now. Some of the higher-end adapters like the Movietube are able to use a relay lens to bypass the camera's attached lens (on cameras like the Canon XL-H1 or JVC GY-HD110U) - I'm not sure of the specifics of how that works, but I think that the idea is to minimize the amount of glass that light has to pass through to get from the adapter to the CCDs.

> 3. What are the benefits? The CCD/CMOS sensor sizes seem to match 16mm and built in lenses are fast enough to handle semi shallow DOF.

The CCD/CMOS sensors on most pro-sumer cameras are far smaller than 16mm frames, even Super-8 frames. Achieving shallow DOF in most practical situations is very difficult - at least nothing that remotely resembles that of 35mm film's capabilities. Even shooting wide open (which is not good in terms of lens sharpness, not to mention can require a healthy stack of ND filters) at F/1.6-1.8, as most of these cameras are capable of, generally requires you to zoom in for a tight shot to maximize the out-of-focus background to aid the shallow DOF effect.

If you take a look through some of the sample footage on the various manufacturers' sites, you'll see some comparisons with and without the adapters - in my opinion, these adapters are the single biggest thing that you can do with a pro-sumer camera to achieve a "cinematic" look.

> 4. Will non-adaptor and adaptor footage intercut well (not in the same scene/sequence)? Or will it look so different from the ground glass adapter vs. just with the built-in lens that the audience would notice. Not just in the same scene, but different scenes/sequences. In film world that would equate either using different stock in different scenes, or a B-camera thats different from A-camera.

It can be done, and I think that the different stock analogy holds well. At some point I stumbled upon a short film named "Katrina" through the SGPro website that does this on some night exterior shots (they removed the adapter due to lack of light), and it looked OK to me, though I'm definitely not an impartial judge since I was looking for the difference in effect.

> 5. How many stops of light do these things loose? Even if using a T1.3 it would seem that the Adapter + Built in Lens would take out about 2-3 stops more making them hard to use in Low Light situations.

It depends on the particular model (and for some, also on the diffuser that's used), but it generally ranges from 1-3 stops. The Cinevate Brevis35 totes the least light loss with their standard adapter (about 1 stop).

> 6. If it is a ground glass, how often do you have to clean it so that you don't end up with dust in the frame?

Not sure, but dust is definitely a concern. I've seen footage with obvious dust, and for professional shoots I think it necessitates a high-resolution, high-quality monitor to spot it before it ruins footage. I'm not sure that dust will cause a problem on all of the models out there, but it definitely will for ones with interchangeable diffusers like the Brevis35.
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#3 Dennis Kisilyov

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Posted 15 February 2007 - 03:15 AM

Troy,

Thanks so much for the info. It helps a lot!

Thanks again.

-DK
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#4 Troy Warr

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Posted 15 February 2007 - 06:09 PM

Not a problem, glad I could help. :)

A few of the adapter manufacturers' sites also feature forums that provide a lot of information, footage samples, workflow issues, etc.
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